(C++) QtExample31

 

 

Qt example 31: moveable thin lines is a Qt example to create some lines that are moveable. Note that because the lines are one pixel thin, it is difficult to really move them! QtExample32 solves this problem.

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 15.04 (vivid)

IDE(s):

• Qt Creator 3.1.1

Project type:

• GUI application

C++ standard:

• C++11

Compiler(s):

• G++ 4.9.2

Libraries used:

• Qt: version 5.4.1 (32 bit)
• STL: GNU ISO C++ Library, version 4.9.2

 

 

 

 

 

Qt project file: ./CppQtExample31/CppQtExample31.pro

 

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exists(../../DesktopApplication.pri) {   include(../../DesktopApplication.pri) } !exists(../../DesktopApplication.pri) {   QT += core gui   greaterThan(QT_MAJOR_VERSION, 4): QT += widgets   TEMPLATE = app   CONFIG(debug, debug|release) {     message(Debug mode)   }   CONFIG(release, debug|release) {     message(Release mode)     DEFINES += NDEBUG NTRACE_BILDERBIKKEL   }   QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra   unix {     QMAKE_CXXFLAGS += -Werror   } } exists(../../Libraries/Boost.pri) {   include(../../Libraries/Boost.pri) } !exists(../../Libraries/Boost.pri) {   win32 {     INCLUDEPATH += \       ../../../Projects/Libraries/boost_1_55_0   } } SOURCES += \     qtmain.cpp \     dialog.cpp \     qtarrowswidget.cpp \     qtarrowitem.cpp HEADERS += \     dialog.h \     qtarrowswidget.h \     qtarrowitem.h FORMS += dialog.ui

 

 

 

 

 

./CppQtExample31/dialog.h

 

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#ifndef DIALOG_H #define DIALOG_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QDialog> #pragma GCC diagnostic pop namespace Ui {   class Dialog; } class Dialog : public QDialog {   Q_OBJECT      public:   explicit Dialog(QWidget *parent = 0);   Dialog(const Dialog&) = delete;   Dialog& operator=(const Dialog&) = delete;   ~Dialog() noexcept;      private:   Ui::Dialog *ui; }; #endif // DIALOG_H

 

 

 

 

 

./CppQtExample31/dialog.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include "qtarrowswidget.h" #include "dialog.h" #include "ui_dialog.h" #pragma GCC diagnostic pop Dialog::Dialog(QWidget *parent) :     QDialog(parent),     ui(new Ui::Dialog) {   ui->setupUi(this);   ui->layout->addWidget(new QtArrowsWidget); } Dialog::~Dialog() noexcept {   delete ui; }

 

 

 

 

 

./CppQtExample31/qtarrowitem.h

 

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#ifndef QTTEXTPOSITIONITEM_H #define QTTEXTPOSITIONITEM_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QGraphicsLineItem> #pragma GCC diagnostic pop struct QtArrowItem : public QGraphicsLineItem {   QtArrowItem(     const double x1,     const double y1,     const bool tail,     const double x2,     const double y2,     const bool head,     QGraphicsItem *parent = 0);   protected:   ///Paint a QtTextPositionItem   void paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *);   ///The rectangle that determines the edges of the item   QRectF boundingRect() const;   ///Show arrow at head   const bool m_head;   ///Show arrow at tail   const bool m_tail; }; #endif // QTTEXTPOSITIONITEM_H

 

 

 

 

 

./CppQtExample31/qtarrowitem.cpp

 

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#include <iostream> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QCursor> #include <QFont> #include <QGraphicsSceneMouseEvent> #include <QPainter> #include "qtarrowitem.h" #pragma GCC diagnostic pop QtArrowItem::QtArrowItem(   const double x1,   const double y1,   const bool tail,   const double x2,   const double y2,   const bool head,   QGraphicsItem *parent)   : QGraphicsLineItem(x1,y1,x2,y2,parent),     m_head(head),     m_tail(tail) {   this->setFlags(QGraphicsItem::ItemIsMovable); } QRectF QtArrowItem::boundingRect() const {   return QRectF(this->line().p1(),this->line().p2()); } void QtArrowItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *) {   painter->drawLine(this->line()); }

 

 

 

 

 

./CppQtExample31/qtarrowswidget.h

 

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#ifndef QTTEXTPOSITIONWIDGET_H #define QTTEXTPOSITIONWIDGET_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QGraphicsView> #pragma GCC diagnostic pop struct QtArrowsWidget : public QGraphicsView {   QtArrowsWidget(); }; #endif // QTTEXTPOSITIONWIDGET_H

 

 

 

 

 

./CppQtExample31/qtarrowswidget.cpp

 

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#include <cassert> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QGraphicsScene> #include <QGraphicsPixmapItem> #include "qtarrowitem.h" #include "qtarrowswidget.h" #pragma GCC diagnostic pop QtArrowsWidget::QtArrowsWidget() {   QGraphicsScene * const scene = new QGraphicsScene(this);   this->setScene(scene);   const int n_lines = 10;   for (int i=0; i!=n_lines; ++i)   {     const double x1 = ((static_cast<double>(std::rand()) / static_cast<double>(RAND_MAX)) * 600.0) - 300.0;     const double y1 = ((static_cast<double>(std::rand()) / static_cast<double>(RAND_MAX)) * 400.0) - 200.0;     const bool tail = (std::rand() >> 4) % 2;     const double x2 = ((static_cast<double>(std::rand()) / static_cast<double>(RAND_MAX)) * 600.0) - 300.0;     const double y2 = ((static_cast<double>(std::rand()) / static_cast<double>(RAND_MAX)) * 400.0) - 200.0;     const bool head = (std::rand() >> 4) % 2;     QtArrowItem * item = new QtArrowItem(x1,y1,tail,x2,y2,head);     scene->addItem(item);   } }

 

 

 

 

 

./CppQtExample31/qtmain.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QApplication> #include <QDesktopWidget> #include "dialog.h" #pragma GCC diagnostic pop int main(int argc, char *argv[]) {   QApplication a(argc, argv);   Dialog w;   {     //Resize the dialog and put it in the screen center     w.setGeometry(0,0,600,400);     const QRect screen = QApplication::desktop()->screenGeometry();     w.move( screen.center() - w.rect().center() );   }   w.show();   return a.exec(); }